Cách sử dụng mặt bích hàn đúng cách

Welding flanges are widely used in piping systems across industries such as oil and gas, hóa dầu, phát điện, xử lý nước, và đóng tàu. They provide a reliable connection between pipes, van, và thiết bị, ensuring mechanical strength and leak-free performance. Tuy nhiên, to achieve these benefits, welding flanges must be used correctly. Improper handling, hàn, or installation can lead to joint failure, Sự rò rỉ, or reduced service life.

This article explains how to use welding flanges correctly, covering preparation, welding techniques, điều tra, and maintenance to ensure long-term reliability and compliance with industry standards.

What Is a Welding Flange

A welding flange is a type of pipe flange designed to be permanently attached to the pipe by welding. The two most common types are:

Mặt bích cổ hàn (WN) – Features a long tapered hub for butt welding to the pipe, offering superior strength and stress distribution.
Mặt bích trượt (VÌ THẾ) – Fits over the pipe end and is fillet welded both inside and outside, easier to install but suitable for lower-pressure service.

Tại sasa thuôn dài, welding flanges are manufactured to meet ASME, EN, DIN, và các tiêu chuẩn quốc tế khác, ensuring compatibility and performance in various industrial applications.

Step-by-Step Guide to Using Welding Flanges Correctly

1. Select the Right Welding Flange

Khả năng tương thích vật liệu – Match flange material to the pipe material to avoid galvanic corrosion and ensure weld quality.
Lớp áp lực – Choose according to system pressure (ví dụ., Lớp học 150, Lớp học 300, Lớp học 600).
Loại mặt bích – Weld neck for high-pressure/high-temperature systems, slip-on for low-to-medium pressure systems.
Tuân thủ tiêu chuẩn – Follow ASME B16.5, ASME B16.47, EN 1092-1, or other applicable standards.

2. Prepare the Pipe and Flange

Check Dimensions – Ensure bore size, outer diameter, and bolt holes match the mating flange.
Làm sạch bề mặt – Remove rust, dầu, dầu mỡ, and dirt from both the pipe and flange.
Bevel the Pipe End – For weld neck flanges, bevel the pipe to the correct angle for butt welding.
Inspect for Defects – Ensure there are no cracks, vết lõm, or other defects on the flange sealing face.

3. Align the Flange and Pipe

Proper Alignment – Misalignment can cause stress concentration, Sự rò rỉ, và thất bại sớm.
Use Alignment Tools – Spacers, jigs, or pipe alignment clamps help maintain accuracy.
Match Bolt Holes – Ensure the bolt holes are in the correct orientation before welding.

4. Welding Procedure

Qualified Welders – Only certified welders should perform welding according to WPS (Đặc điểm kỹ thuật quy trình hàn).
Preheating – Some materials, such as alloy steels, require preheating to prevent cracking.
Weld Type:
- Butt Weld for weld neck flanges – Provides a smooth internal bore for fluid flow.
- Fillet Weld for slip-on flanges – Requires welding on both the inside and outside.
Multiple Pass Welding – For thicker flanges, apply multiple passes to ensure complete penetration.
Avoid Overheating – Excess heat can distort the flange or damage sealing surfaces.

5. Kiểm tra sau hàn

Kiểm tra trực quan – Check for cracks, sự cắt xén, độ xốp, or incomplete fusion.
Kiểm tra không phá hủy (NDT) – Use ultrasonic testing (UT), magnetic particle testing (MT), or liquid penetrant testing (PT) as required by the project specification.
Dimensional Check – Verify that the flange remains within tolerance after welding.

6. Gasket Installation and Bolt Tightening

Lựa chọn miếng đệm – Choose the correct gasket type (vết thương xoắn ốc, khớp kiểu vòng, soft gasket) for the service condition.
Bolt Lubrication – Apply approved lubricant to threads and nut faces for accurate torque.
Tightening Pattern – Use a cross or star pattern in multiple passes to ensure even compression.
Kiểm soát mô-men xoắn – Follow specified torque values for the bolt size, vật liệu, và loại đệm.

7. Kiểm tra áp suất

Kiểm tra thủy tĩnh – Checks for leaks at a pressure higher than operating pressure.
Kiểm tra khí nén – Used for low-pressure systems or where water is unsuitable.
Safety Precautions – Always follow safety standards when performing pressure tests.

8. Bảo trì và kiểm tra

Regular Checks – Kiểm tra các bu lông, miếng đệm, and sealing surfaces periodically.
Phòng chống ăn mòn – Apply protective coatings or anti-corrosion tape if exposed to harsh environments.
Re-Torque Bolts – For systems subject to vibration or thermal cycling, bolts may need re-tightening during initial operation.

Common Mistakes to Avoid When Using Welding Flanges

Incorrect Material Selection – Leads to corrosion or thermal expansion mismatch.
Poor Alignment – Causes leakage and uneven gasket compression.
Over-Tightening Bolts – Damages gaskets and sealing surfaces.
Skipping NDT – Increases the risk of undetected weld defects.
Inadequate Cleaning – Oil, rỉ sét, or debris can compromise weld quality and sealing.

Advantages of Correct Welding Flange Usage

Leak-Free Connections – Proper welding and bolt tightening ensure tight seals.
Tuổi thọ phục vụ kéo dài – Minimizes wear and corrosion.
Cường độ cao – Welding creates a permanent, strong bond between pipe and flange.
Tính linh hoạt – Suitable for various pressure classes, nhiệt độ, and environments.

Phần kết luận

Using welding flanges correctly involves more than just attaching them to a pipe. From selecting the right flange type and material to proper welding, điều tra, và bảo trì, every step must follow strict industry standards and best practices. When installed and maintained correctly, welding flanges deliver excellent sealing performance, tính toàn vẹn cấu trúc, and long service life in industrial piping systems.

With expertise in manufacturing high-quality welding flanges and providing technical guidance, sasa thuôn dài ensures that customers get reliable, tuân thủ, and durable flange connections for even the most demanding applications.